Acetyl cellulose and process of making the same



UNITED STATES PATENT OFFICE.

WILLIAM GODSON LINDSAY, 0F NEWARK, NEW JERSEY, ASSIGNOR TO THE CELLULOID1 COMPANY, A CORPORATIONDF NEW JERSEY.

ACETYL CELLULOSE AND PROCESS OF MAKING THE SAME. 7

Specification of Letters Patent.

Patented'Apr. 27, 1920.

no Drawing. Original application filed April 8, 1911, Serial No.619,685. Patent No..1,236,5 78, dated August 14, 1917. Divided andapplication filed July 11, 1914, Serial No. 850,431. Patent No.

1,265,216, dated May 7, 191a. Divided and this To all whom it mayconcern Be it known that I, WILLIAM Gonson LIND- SAY a citizen ofthe'United States, residing Newark, in the, county of Essex and State ofNew 'Jersey, have invented certain new and useful Improvements in AcetylCellulose and Processes of Making the Same, of which the following is aspeclfication.

This application relates to acetyl cellulose and a process of making thesame, This a plication is a division of my application, S drial No.850,431, filed July 11, 1914, Wh1ch as eventuated in Patent No.1,265,216, dated May 7 1918, and which in turn was a division of myapplication, Serial No. 619,685, filed A ril 8, 1911, which haseventuated as Patent 1 o. 1,236,57 8, dated August 1 1, 1917. It is wellknown that, while acetyl cellulose is a desirable substance forreplacing nitrocellulose in many applications, the special difficultiesconnected with its manufacture have, in large part, prevented itsadpption for practical purposes. '1. he acetylatlon of cellulose is sosensitive to the influence of acetylizing mixtures and physicalconditions that up to the present time it has been hard to produce adefinite, and uniform product.

'lhe principal difliculty has been the production of acetyl cellulosehaving a con served strength of fiber'and such a definite solubility aswould fit it for use with certain solvents, or for application toparticularpurposes in the arts.

Previous to my invention the products of the various processes proposedhave been strictly circumscribed because of their defects or practicallimitations. For example, the acetyl cellulose would be in one caselimited to the amorphous form anda defijnite solubility. In another casethe form would be similarly limited, but the solubility would have awider range. In another case the result would be a fibrous acetylcellulose, but weak and. brittle. In still another case there would be abetter conservation of the fibrous form,but a 1imited solubility ordegree of acetylization.

The varying steps of manufacture are,

application filed April 9, 1918. Serial No. 227,488.

propose produces acetyl cellulose having new'characteristics. Inpractice I proceed as follows:

Cellulose, preferably a high grade bleached cotton, is given apreliminary treatment with acetic acidgf about 75% to 98% until thecotton is thoroughly impreg nated. The mixture of cotton and acetic acidis then introduced into the acetylizing' ing varied according to theminor conditions of operating hereinafter described.

To some extent I control the solubility of my product, either bychanging the strength of the acetic acid used'in'the preliminary bath,or by varying the amount of acid used in proportion to the fiber. Forexample, when using about 200 parts of acid to 100 parts of fiber, Iemploy acetic acid varying from about 75% to 98%. When using an 85%acetic acid as a constant strength I employ, say, from about 70 to 250parts to each 100 parts of the fiber.- By this means I can produce anacetyl cellulose soluble in a mixture of chloroform and alcohol, butincompletely soluble in chloroform alone; or a variety which is quiteviscous in acetone, or one which produces more fluid solutions, Someof Imy ,acetyl .cellulose is freely, soluble, sin- 3. acetylene tetrachlorid,

while some requires the addition of alcohol before the acetylenetetrachlorid will make a complete solution.

, I also vary the solubility in different solvents by changes in theproportion of-sulfuric acid in the acetylizing mixture. and also bymeans of time of contact and the temperature, as is generallyunderstood.

So far as I can ascertain, the preliminary treatment above describedproduces no chemical effect upon the fiber, but simply puts it into abetter condition for the subsequent "reaction; In other words, when thefiber enters the acetylizing mixture it is still ordinary cellulose.

I have also discovered certain equivalents of the acetic acid for mypreliminary treatilar to nitrated cotton'in which the str engt harsh tothe touch and practically ment. F or'example, if the. water in theacetic acid be replaced by alcohol, eithier t e ethyl or methyl, theeffect is apparentl.

same. Or, in place of the acetic acid, can hse a mixture of benzene andethyl or methyl alcohol, in which case the benzene will represent thepure acetic acid,anll the alcohol will represent the water. .Ortheacetic acid can be replaced by ethyl .acetate of similar strength; orfIma use, say, a mixture .of-ethyl acetate and either ethyl or methylalcohol, in which case ethyl acetate able for the manufacture of'thin-sheets, 75

' or, after being rendered plastic 'by'the addireplaces the pure aceticacid and the alcohols act in place of the water. In, fact, in place ofthis acetic acid I can use any substance whatever, so long as suchsubstance acts in a similar way to protect the cotton fiber fromtheinitial violent attack of the acet lizing mixture. This protection isaffor ed by what might be called a diluting" or shielding of thecottonfiber by means of a liquid that is compatible, but nevertheless does notreadily react with acetic anhydrid and sulfuric acid, but tends toregulate or prolong the initial reaction. Water alone would not be sucha 1i uid, because it would increase the violence 0 the first attack.

In order to. still 'further instruct the operator, I give the followingproportions and conditions as a specific example of my improved process.Upon 100 parts by weight of pure cotton rovingseis poured 200 parts of90% acetic acid. After the acid has become uniformly spread throughoutthe 111 885,111? mixture -is introduced into a bath consistingof 600parts of acetic anhydrid, 25

' parts of 96%v sulfuric acid, and 1400 parts four hours, at the end ofwhich time, if the i in hot and lulos'e.

of benzene, at a'temperature of about 50 F.

' stood, of course, that I can use other vege- 105 The acetylation isthen allowed to proceed at a temperature of about F. for twentyconditiongiven be properly observed, a test portion should be soluble in amixture'of acetylene tetrachlorid and alcohol, dichlor-i hydrin,epichlorhydrin, or nitrobe nzene.

The excess ofthe reaction-mixture is then removed by any suitable means;for example, by whizzing or by pressing. The acetyl cellulose is thenimmersed for one hour in a hot solution of calcium nitrate (consistingof about one pound to the gallon), after which it is thoroughly washed,preferably then in cold water, and .then

dried.

The object ofthis treatment with calciuni' I nitrate is to remove anyfree sulfuric acid adhering to the fiber, and. also to neutralize anysulforiic acid ester that might accompany the formation of the acetylceltion of the solvents mentioned, it can be manipulated so as toproduce other forms. 7 The acetyl cellulose made by the formula justdescribed has an increase from the 001- 80. lulose to'the final productof about 65%. In general, the increase of weight bears some relationtovariations in solubilit and depends upon the character of the firstsolu' tion and the conditions of acetylization. In

practice the increase obtained by my rocess has varied from 50% to 80%an even higher.

As to this influence of the acetylizing mixture and the conditions ofacetylization', I might add that increase in weight is pro duced byprolonged reaction. The temperature will also have its eifect. But inall cases the influence of the acetic acid into which the cotton isfirstimmersed is greater 7 than the effect of the acet lizing mixture,-or

- time and temperature. therefore call the operators attentionespecially to the importance of'this first ste in my process.

The proportion o sulfuric acid inthe acetylizing mixture is also of someimportance in controlling the variety of acetyl celulose produced. WhileI prefer'to use cellulose in the form of cotton, it is' undertablefibers suitabl prepared.

The acetyl cellu ose made by my process does not consist of any one varety or degree of acetylation. It is not, for example, di-,

or trior tetraacetyl cellulose. And this. very mixture or combination isofgreat practical importance, as furnishin'g products specially'suitablefor industrial applications. j

Having thus described my invention; I declare that what I claim as newand desire to secure by Letters Patent is: a

1. The process of producing acetyl cellulose, which consists in treatingcellulose lose, which consists in treating with benzene and alcohol, andthen subjecting the impregnated cellulose to 'an acety-' lizin mixturecontaining acetic anhydrid and enzene.

2. The process of producing acetyl celluwith benzene, and alcohol, andsubjecting the impregnated cellulose to'an acetylizing mixture;

- WILLIIAM GODSQN LINDSAY.

cellulose m5

